Check that Flash Player is actually working by trying to view a random Youtube video. If it isn't, uninstall 'Adobe Flash Player Plug-in', restart your computer and then reinstall Flash Player from here:
http://get.adobe.com/flashplayer/
If Flash Player is working the problem might well be with one or more sites which actually host the videos that you're seeking. There are no videos actually hosted on the Couchtuner.eu website; it merely functions as an 'index' site, directing you to places on the internet where the programme files are actually hosted. Those sites are almost certainly operating outside the law (since they won't hold the international broadcast rights for the programmes and won't pay any money to the companies who make the programmes). So it should hardly be viewed as surprising if they're forced to shut down, with the resultant loss of their content to potential viewers.